I asked Aba Abdillah Imam Sadiq (as), 'I meet a Zimmi (non-muslim staying in an Islamic country) and he shakes hands with me. Imam (as) said, "Wipe it (hand) with sand or against the wall.

I said, "Then if its a Nasibi (one who has enmity with AhlulBait (as) and their Shias)?" Imam (as) said, "Wash it (hand)"

[Source: al-Kafi, Vol.2, Pg. 650, Hadith. 11]

Check out the verses of the Quran, Chapter. 5, Verse. 58 to 61 - These verses prove that the hypocrites (who claim to be Muslims but don't believe from their heart) are worse than the Jews and Christians who oppose Islam and Muslims.